PRO-4 TM TRIMMER LINE - Pro-4 TM is a unique square shaped, yellow line. The 4 sharp edges create a clean, fast and smooth cut. Pro-4"s excellent cutting capability and extreme wear resistance enable users to complete bigger jobs in less time. Pro 4 is a commercial high grade co-polymer line that is excellent for commercial users and consumers who want great quality at an affordable price. Made in the U.S.A.